Sen. Mark Dayton fired an aide who established a constituent hotline because he was sleeping on the job, Senate lawyers working on behalf of the Minnesota Democrat said in response to a lawsuit filed by the former employee.

The allegation marked the first public and most aggressive explanation by Dayton for the termination of Brad Hanson, a 49-year-old aide who had been publicly praised by the lawmaker for his work on the campaign and in the Congressional office before he was fired last year.

Hanson has sued Dayton, alleging he was wrongly fired after he informed Dayton that he needed to take leave for a few weeks to recuperate from a cardiac procedure.

In another twist, Dayton confirmed that he had paid Hanson $1,000 a month from personal funds to cover Hanson’s insurance premiums after he was terminated. The payments, reported Friday by the Minneapolis Star-Tribune, were made even after Hanson filed his lawsuit in May and continued until last month, a Dayton spokeswoman confirmed.

The case is the latest test of the limits of the 1995 Congressional Accountability Act, which purportedly gave Congressional staff the right to go to court to enforce 11 workplace and safety laws that apply to every other employer.

Dayton, through Senate lawyers, has claimed he enjoys special immunity under the Constitution’s Speech or Debate Clause, and the two legal briefs filed on his behalf focus on convincing U.S. District Judge Richard Leon to dismiss the case on those grounds.

But in a footnote to a brief filed last week, Senate Employment Legal Counsel Jean Manning stepped beyond the largely procedural arguments and addressed the specific merits of the case, calling Hanson’s allegations “false.”

“Hanson was terminated because of his exceptionally poor job performance and his inability to fulfill his job responsibilities; indeed, he literally slept on the job,” the brief charged.

“Senator Dayton takes seriously his responsibilities to Minnesotans and does not continue to employ those who do not,” the footnote added.

Hanson’s attorney, Richard Salzman, called the allegation “absolutely ludicrous. It’s not true.” He said there was never any indication that Dayton was unhappy with Hanson’s job performance.

He said his client is even more anxious now to get the merits of his case before a court to disprove Dayton’s allegation. “We certainly wish the Senator, if he feels like he had a legitimate reason to fire Brad, would go to court and try to prove it instead of seeking immunity through this really arcane argument that we think is just absolutely wrong,” Salzman said.

Despite the ongoing litigation, Dayton’s chief of staff, Sarah Dahlin, issued a written statement amplifying the allegation leveled in the footnote.

“Brad Hanson was fired because he did not do his job,” Dahlin said. “Having consistently failed to meet the needs of constituents, including not taking care of individual requests for help from over 100 Minnesotans, Brad Hanson was asked to leave the office.

“Brad’s claim that Mark took action against him because of a health problem is absolutely untrue and completely inconsistent with Mark’s response to staff members who have faced a health crisis.”

Dahlin pointed to three other staff members who required extended leave because of health problems.

“In each case, Mark personally assured the staff member their job was secure no matter how long they needed to be out of the office for treatment and recovery. To assert that Mark would take action against an employee for any sort of health problem is absolutely preposterous,” she said.

Salzman said that no one from Dayton’s staff ever expressed dissatisfaction with Hanson’s work and had never said anything about sleeping on the job. “Brad was a really hard-working, dedicated employee who put in a tremendous amount of time and was quite valued. He was a guy who was engaged, trusted by the Senator and worked hard for him,” Salzman said, adding that the two men and their families had been friends for the past 14 years.

Dayton’s aggressive response came even as Minnesota Republicans criticized the legal position Dayton has laid out in court papers.

“This is not exactly the kind of motion you would expect from a Senator who has billed himself as a friend and defender of working Minnesotans,” said state GOP spokesman Randy Wanke. “Here’s a guy who is using the defense that because he’s a United States Senator he doesn’t have to abide by federal labor laws.”

Salzman confirmed that Dayton had made payments to Hanson to cover his medical insurance once he left the Senate payroll, but he insisted that Dayton’s largess did not undercut Hanson’s claim that he was wrongly fired.

“Our view is that the Senator felt bad about what he did and was trying to ameliorate it to some extent,” Salzman said. “Brad appreciates that he continued to pay his health insurance, but that doesn’t make up for the fact that he fired him.”

Dayton’s spokeswoman, Chris Lisi, said the payments were made for a year. “They had a one-year deal, if you will. Basically, Brad asked for a lot of things when he left,” Lisi said. In addition, Dayton provided a family membership to a spa, she said.

The Star-Tribune also reported that Salzman’s firm had sent a letter to Dayton’s office in December saying that the litigation could be settled with a payment of $500,000.

“Mr. Hanson and you have had a lengthy relationship, and he has no desire to cause you any discomfort, either personally or politically,” wrote another attorney for Hanson, Douglas Huron, according to the Star-Tribune.

Salzman said he was surprised to see the letter reported because it was part of the confidential remediation process required by the Congressional Accountability Act.

He said it is normal practice in litigation for a lawyer to contact the other side to lay out the case and suggest settlement terms. “But the unique thing about the Congressional Accountability Act is that all of that is supposed to be shrouded in statutorially imposed secrecy, which I can assure you we have adhered to. I don’t know how that came out, but I can guess,” Salzman said.

Lisi declined to provide a copy of the letter, citing legal reasons.